const fs = require('fs')
const util = require('util')
const path = require('path')
const { siteUrl, siteTitle, siteDescription, author } = require('../config')
const writeFile = util.promisify(fs.writeFile)

const feedContent = (edge) => {
  const { image } = edge.node.frontmatter
  const { html } = edge.node
  const footer =
    '<hr />This post was published on <a href="https://kremalicious.com">kremalicious.com</a>'

  return image
    ? `<img src="${image.childImageSharp.resize.src}" /><br />${html}${footer}`
    : `${html}${footer}`
}

async function jsonItems(posts) {
  return await posts.map((edge) => {
    const { frontmatter, fields, excerpt } = edge.node
    const { slug, date } = fields

    return {
      id: path.join(siteUrl, slug),
      url: path.join(siteUrl, slug),
      title: frontmatter.title,
      summary: excerpt,
      date_published: new Date(date).toISOString(),
      date_modified: frontmatter.updated
        ? new Date(frontmatter.updated).toISOString()
        : new Date(date).toISOString(),
      tags: [frontmatter.tags],
      content_html: feedContent(edge)
    }
  })
}

const createJsonFeed = async (posts) => ({
  version: 'https://jsonfeed.org/version/1',
  title: siteTitle,
  description: siteDescription,
  home_page_url: siteUrl,
  feed_url: path.join(siteUrl, 'feed.json'),
  user_comment:
    'This feed allows you to read the posts from this site in any feed reader that supports the JSON Feed format. To add this feed to your reader, copy the following URL — https://kremalicious.com/feed.json — and add it your reader.',
  favicon: path.join(siteUrl, 'favicon.ico'),
  icon: path.join(siteUrl, 'apple-touch-icon.png'),
  author: {
    name: author.name,
    url: author.uri
  },
  items: await jsonItems(posts)
})

const generateJsonFeed = async (posts) => {
  await writeFile(
    path.join('./public', 'feed.json'),
    JSON.stringify(await createJsonFeed(posts)),
    'utf8'
  ).catch((err) => {
    throw Error('\nFailed to write JSON Feed file: ', err)
  })

  console.log('\nsuccess Generating JSON feed')
}

module.exports = { generateJsonFeed, feedContent }